1. Field of the Invention
The present invention relates to a fuel pump control device, and more particularly to a fuel pump control device allowing a fuel pump having a small capacity to feed a sufficient amount of fuel to an internal combustion engine.
2. Description of Background Art
As described in Japanese Utility Model Publication Nos. Hei 2-31566 and Hei 6-14069, control devices for controlling an electrically-operated fuel pump for feeding fuel to an internal combustion engine have been configured such that a relay means is connected between the fuel pump and a battery, wherein the fuel pump is intermittently operated by opening/closing the relay means on the basis of an ignition signal for an engine.
FIG. 4 is a block diagram showing an essential portion of the above-described related art fuel pump control device. Referring to FIG. 4, a fuel pump control device 3 includes a thyristor (SCR) 301 as a relay means and an ignition circuit 302. The thyristor 301 is connected, together with an-ignition switch 2, in series between a fuel pump 6 and a battery 1. An ignition coil 5 and an ignitor 4 connected in series to each other are connected in parallel to the battery 1 via the ignition switch 2. An ignition pulse is supplied from the ignition coil 5 to the ignition circuit 302. Accordingly, the thyristor 301 is opened/closed one time for each ignition of the engine, to thereby intermittently drive the fuel pump.
The thyristor 301 as the relay means, which has no mechanical contact, is excellent in durability; however, it has a large voltage drop xcex94V at a PN junction. As a result, a drive voltage applied to the fuel pump 6 is lower than a battery voltage by the voltage drop xcex94V. On the other hand, as shown in FIG. 5, since the feeding ability of the fuel pump is, generally, largely dependent on a drive voltage. Accordingly, if the drive voltage is reduced as described above, the fuel pump cannot feed a sufficient amount of fuel. For this reason, in the case of adopting the thyristor as the relay means, there occurs a problem that it is required to use a fuel pump having a large capacity, that is, a large-sized, expensive fuel pump for feeding a sufficient amount of fuel even if the drive voltage applied to the fuel pump is lower than the battery voltage.
An object of the present invention is to solve the problem of the above-described related art fuel pump control device and to provide a fuel pump control device allowing a fuel pump having a small capacity to feed a sufficient amount of fuel to an internal combustion engine.
To achieve the above object, the present invention provides the following configurations:
(1) a fuel pump control device for intermittently supplying a drive signal, to an electrically-operated fuel pump for feeding fuel to an internal combustion engine, in synchronization with an ignition signal for the internal combustion engine, characterized in that a drive signal is continuously supplied to the fuel pump in accordance with a running state of a vehicle; and
(2) a fuel pump control device for controlling an electrically-operated fuel pump for supplying fuel to an internal combustion engine, characterized in that the control device comprises: a vehicle running state deciding means for generating a vehicle running state signal representative of a running state of a vehicle; a comparing means for comparing the vehicle running state signal with a specific value, and a controlling means for controlling opening/closing of the connection between the fuel pump and a power supply line in accordance with the comparison result obtained by the comparing means.
According to the above-described first feature, a drive signal is continuously supplied to the fuel pump under a specific, vehicle running state, whereby the fuel pump repeats the discharge operation. Accordingly, it is possible to increase the discharged amount per unit time without enlarging the fuel pump.
According to the above-described feature (2), since the fuel pump is directly connected to the power supply line under a specific vehicle running state, the fuel pump repeats the discharge operation. Accordingly, it is possible to increase the discharged amount per unit time without enlarging the fuel pump.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.